|Publication number||US7274061 B2|
|Application number||US 10/841,686|
|Publication date||Sep 25, 2007|
|Filing date||May 6, 2004|
|Priority date||Jun 3, 2003|
|Also published as||US6964901, US7274059, US7414297, US20040245559, US20040245560, US20060252201, US20080012093|
|Publication number||10841686, 841686, US 7274061 B2, US 7274061B2, US-B2-7274061, US7274061 B2, US7274061B2|
|Inventors||Marsela Pontoh, Cem Basceri, Thomas M. Graettinger|
|Original Assignee||Micron Technology, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Classifications (27), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This patent application is a divisional application of U.S. Patent Application No. 10/454,302 filed on Jun. 6, 2003, now U.S. Pat. No. 6,964,901.
The invention pertains to capacitor constructions comprising rugged materials, and pertains to methods of forming rugged electrically conductive surfaces and layers.
Rugged surfaces are utilized in numerous semiconductor constructions. For instances, rugged silicon-containing surfaces are frequently utilized as electrodes of capacitor constructions. The rugged surfaces can increase the surface area of the electrodes, and can thereby increase the amount of capacitance per unit surface area of the electrodes relative to a non-rugged surface. An exemplary form of rugged silicon is hemispherical grain (HSG) silicon.
Various problems can exist during the integration of rugged silicon into capacitors and other semiconductor devices. For instance, the conductivity and other physical properties of silicon are frequently not as good as those associated with other conductive materials, such as, for example, metal-containing materials. Accordingly, there would be advantages to utilization of metal-containing materials in place of rugged silicon. Unfortunately, it is typically difficult to form a rugged surface associated with a metal-containing material. Thus, if the improved properties of metal-containing compositions are desired in a semiconductor structure, such properties are typically obtained at the expense of utilizing a material lacking a rugged surface. It would therefore be desirable to develop methodology for forming metal-containing materials having rugged surfaces. It would be further desirable to incorporate such materials into semiconductor constructions, such as, for example, capacitor constructions.
Although methodology of the present invention was developed in light of the above-described desired aspects, it is to be understood that the methodology is not limited to such aspects. Accordingly, methodology of the present invention can be utilized not only for forming metal-containing materials having rugged surfaces, but can also be utilized for forming other materials having rugged surfaces.
In one aspect, the invention pertains to a method of forming a rugged electrically conductive surface. A composition is formed as a continuous layer across an electrically insulative surface of a substrate. The continuous layer is at least partially dissociated to form gaps extending to the electrically insulative surface. An electrically conductive surface is formed to extend across the dissociated layer and within the gaps. The electrically conductive surface has a rugged topography imparted by the dissociated layer and the gaps.
In another aspect, a method of forming a rugged electrically conductive surface comprises forming a silicon-containing layer across a substrate, and subsequently dissociating at least a portion of the silicon-containing layer into a plurality of structures spaced from one other by gaps extending to the substrate. An electrically conductive surface is formed to extend across the structures and across the gaps between the structures, with such surface having a rugged topography imparted by the structures and gaps.
In another aspect, the invention encompasses a capacitor construction. The construction includes a plurality of spaced islands (also referred to herein as seeds) over a substrate, with the islands having silicide-containing surfaces. A first conductive material extends between the spaced islands and electrically connects the islands with one another. The first conductive material has a different composition than the islands. A dielectric material is over the first conductive material, and a second conductive material is over the dielectric material. The capacitor construction can be included within dynamic random access memory (DRAM) devices, and the DRAM devices can be included within electrical systems.
Preferred embodiments of the invention are described below with reference to the following accompanying drawings.
This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress to science and useful arts” (Article 1, Section 8).
One aspect of the invention is a recognition that seeds (or islands), and/or partially dissociated materials can be utilized for rough metal formation (with the term “rough metal” referring to a metal having a rugged surface). The seed and/or partially dissociated material can be a semiconductor-containing material, such as, for example, a silicon-containing material. In particular aspects, methodologies traditionally utilized for forming hemispherical grain silicon can be utilized to form the seed and/or partially-dissociated material of the present invention. The rough metal can be utilized in various semiconductor devices, and in particular aspects can be utilized as an electrode in a capacitor. The rough metal can thus replace hemispherical grain silicon in capacitor assemblies.
A first exemplary aspect of the invention is described with reference to
A continuous layer 14 is formed over surface 15, and in the shown aspect of the invention is formed physically against surface 15. The layer is continuous across the shown fragment, and accordingly is continuous over at least a portion of the wafer comprising the shown fragment. The layer may, in particular aspects, be continuous over an entire surface of the wafer, and may, in other aspects, be continuous over only portions of the wafer surface. Layer 14 can comprise any appropriate composition which can be subsequently at least partially dissociated. In particularly aspects, layer 14 comprises, consists essentially of, or consists of silicon. If the composition of layer 14 comprises a semiconductive material (such as, for example, silicon) the composition can be essentially undoped at the processing stage of
Referring next to
It is recognized that separated structures have previously been formed from numerous materials through utilization of patterned masks. Specifically, photolithographic patterning is utilized to form a patterned mask, and then a pattern is transferred from the mask to underlying materials utilizing a suitable etch. For purposes of interpreting this disclosure and the claims that follow, the terms “dissociation” and “breaking up” of layer 14 refer to processes in which the physical separation of layer 14 into spaced structures 16 is caused, at least in part, by something other than a transfer of a pattern from a patterned mask (such as, for example, the above-described annealing). Typically, the dissociation and/or breaking up of layer 14 will be an entirely maskless process, at least no mask will typically be present over the region where structures 16 are formed during the formation of structures 16.
The individual structures 16 are shown separated from one another by gaps 18 which extend to the upper surface 15 of substrate 12. Although all of the structures are equal in size and shape in the shown cross-sectional view, and are shown to be entirely separated from one another, it is to be understood that some of the structures could be different in size and shape relative to one another, and that some of the structures could merge together. Also, it is to be understood that although layer 14 can be broken into discrete islands, the invention encompasses other aspects in which the continuous layer is only partially dissociated to form gaps extending to substrate surface 15, and wherein at least portions of the partially dissociated layer extend around the gaps rather than being broken into discrete islands separated by the gaps.
The amount of dissociation of layer 14, the size of structures 16, and the separation between the individual structures, can be controlled by the initial thickness of layer 14 and the processing temperature and time utilized to dissociate layer 14. As discussed above, layer 14 can, in particular aspects, comprise either doped or undoped silicon. It can be advantageous to utilize undoped silicon, in that it is generally easier to dissociate undoped silicon than doped silicon. However, with suitable processing temperatures and times, doped silicon can also be dissociated to form structures 16.
In subsequent processing (described below) a conductive surface is formed across the structures 16 and the gaps 18 between the structures. The gaps and structures impart a rugged topography to such conductive surface. In some aspects, it can be desirable to treat structures 16 prior to, or during, the formation of such conductive surface. In one aspect, it can be desirable for structures 16 to have an electrically conductive surface suitable for incorporation into the rugged surface which is ultimately formed across substrate 12. If layer 14 (
Layer 20 can comprise any suitable electrically conductive material, and in particular aspects will be a metal-containing layer. Layer 20 can, for example, predominantly comprise one or more metals (with the term “predominantly comprise” indicating that the layer comprises more than 50 atomic percent of the one or more metals), consist essentially of one of more metals, or consist of one or more metals. In particular aspects, layer 20 will predominantly comprise, consist essentially of, or consist of one or more of titanium, tungsten, platinum, rhodium, tantalum, and ruthenium. An exemplary combination of metals that can be utilized in layer 20 is platinum and rhodium. Layer 20 can have any suitable thickness, and in particular aspects will have a thickness of from about 20 Å to about 70 Å.
Layer 20 has an electrically conductive surface 21, and structures 16 have electrically conductive surfaces 23. Surfaces 21 and 23 together define an electrically conductive surface extending across structures 16 and within the gaps 18 between the structures. Such electrically conductive surface has a rugged topography imparted by its undulation over the structures and within the gaps. In particular aspects, the electrically conductive surfaces of the structures 16 can be considered to be first electrically conductive surfaces, the electrically conductive surfaces of the conductive layer 20 can be considered to be second electrically conductive surfaces, and the rugged electrically conductive surface can be considered to be comprised of the first and second electrically conductive surfaces.
The conductive surfaces of the structures 16 can be formed by any suitable method. In some aspects, the conductive surfaces can be formed by converting silicon of the structures to silicide. In other exemplary aspects, structures 16 can comprise a semiconductor (such as silicon), and the conductive surfaces of structures 16 can be formed by providing conductivity-enhancing dopant within semiconductor of the structures to a sufficient concentration to form electrically conductive surfaces of the structures. To the extent that conductivity-enhancing dopant is provided within structures 16, such can be provided by forming conductivity-enhancing dopant within layer 14 at the processing stage of
Layer 20 can be formed by any suitable method, including, for example, atomic layer deposition (ALD), pulsed sequential deposition (PSD), chemical vapor deposition (CVD), etc.
If surfaces 21 and 23 comprise materials which can react with nitrogen-containing precursors to form nitride, (such as, for example, silicon and/or appropriate metals) nitride layer 26 can be formed by exposing the surfaces 21 and 23 to NH3, to N2 to combination with H2, and/or to other appropriate nitrogen-containing precursors. The exposure to the nitrogen-containing precursors can occur in combination with plasma and/or with an appropriate thermal anneal. If surfaces 21 and 23 comprise a metal, and if barrier layer 26 is a nitride-containing material formed by nitridization of the metal from surfaces 21 and 23, the layer 26 will contain at least one metal in common with the surfaces 21 and 23.
Conversion of surfaces 21 and 23 to nitride can occur within the same reaction chamber as is utilized for formation of conductive layer 20 (i.e., in situ with formation of conductive layer 20), or can occur in a separate reaction chamber than that utilized for formation of layer 20 (i.e., ex situ relative to formation of conductive layer 20).
Barrier layer 26 is provided to prevent leakage across silicide of structures 16 relative to the dielectric material 28. In applications in which structures 16 do not comprise silicide, or in which the dielectric material does not comprise a composition in which leakage across a silicide is problematic, barrier layer 26 can be omitted. Particular dielectric materials for which leakage is typically not problematic are silicon nitride/silicon dioxide/silicon nitride (so-called ONO) dielectric layers. Dielectric layers commonly exhibiting leakage problems are the so-called high-K dielectric materials such as, for example, tantalum pentoxide.
Conductive material 30 can comprise any suitable material, including, for example, conductively-doped silicon and/or various metal-containing materials.
A difference between the aspects of the invention shown in
Another aspect of the invention is described with reference to
Material 20 is utilized to convert structures 16 to electrically conductive compositions. In particular aspects, structures 16 will comprise, consist essentially of, or consist of silicon. After formation of layer 18, the structures 16 are subjected to appropriate processing to convert the silicon of such structures to metal silicide. Such metal silicide incorporates one or more metals from layer 18, and is formed by reaction of silicon from structures 16 with metal of material 20. If, for example, layer 18 predominantly comprises titanium, the metal silicide of structures 16 can predominantly comprise titanium silicide.
Although not shown in
Layer 20 comprises upper surface 21, and in the aspect of
Dielectric material 28 and conductive material 30 can comprise the compositions described previously with reference to
The various aspects described above with reference to
A transistor device 104 is supported by base 102. Transistor device 104 comprises a transistor gate 106 over base 102, and source/drain diffusion regions 108 extending into base 102. Gate 106 and source/drain diffusion regions 108 can comprise conventional constructions and materials. The shown gate 106 comprises an insulative layer 110 (such as, for example, silicon dioxide), one or more conductive materials 112 over the insulative material, and an insulative cap 114. Sidewall spacers 116 are shown formed adjacent to gate 106. The source/drain diffusion regions 108 comprise shallow lightly-doped regions 118 under the sidewall spacers 116, and deep heavily-doped regions 120 outwardly of the lightly-doped regions 118.
An isolation region 122 is shown extending into base 102 adjacent one of the source/drain diffusion regions. Isolation region 122 can comprise, for example, a shallow trench isolation region and is utilized for electrically isolating transistor structure 104 from adjacent circuitry (not shown).
A conductive pedestal 124 is formed over one of the source/drain diffusion regions 108, and is in electrical contact with the source/drain diffusion region. The pedestal can comprise any suitable electrically conductive material, including, for example, conductively-doped silicon, metal, and/or metal-containing compounds.
Pedestal 124 has an upper surface 130 which defines an electrical node. It is to be understood that an electrical node can comprise other configurations besides the shown upper surface of pedestal 124. In particular aspects, the pedestal 124 can be eliminated and an upper surface of diffusion region 120 can constitute the electrical node.
An insulative material 126 is formed over base 102. Material 126 can comprise any suitable electrically insulative material, such as, for example, BPSG.
An opening 128 extends through insulative material 126 to upper surface 130 of pedestal 124. Opening 128 comprises a periphery having side surfaces 132, and comprises a bottom surface corresponding to the surface 130 of pedestal 124. The bottom surface of the opening is thus electrically conductive, and the side surfaces 132 are electrically insulative.
Construction 100 can be considered to comprise a substrate, with such substrate including the base 102, and including the electrical node 124 and the insulative material 126 supported by the base. Ultimately, a capacitor construction is formed within opening 128 (in processing described below), and is thus formed in electrical contact with one of the source/drain diffusion regions 108 of transistor construction 104. The other of the source/drain diffusion regions 108 is ultimately connected to a bitline 134. The connection to bitline 134 can occur before or after formation of the capacitor within opening 128.
Structures 16 are separated by gaps 18 which extend to conductive node 130 along the bottom periphery of opening 128, and which extend to insulative material 126 along the sidewall peripheries of opening 128.
A dielectric material 28 is provided over nitride-containing layer 26, and a conductive material 30 is provided over dielectric material 28. Pedestal 124 in combination with conductive materials of structures 16 and layers 20 and 26 can be considered to comprise a first capacitor electrode, conductive material 30 can be considered to comprise a second capacitor electrode capactively separated from the first capacitor electrode by dielectric material 28. Accordingly, the first capacitor electrode, the second capacitor electrode, and the dielectric material 28 can be considered to form a capacitor construction. The capacitor construction is gatedly connected to bitline 134 through transistor construction 104. The capacitor and transistor of
As discussed previously, barrier layer 26 can be particularly advantageous in applications in which there is potential leakage across a silicide in the absence of the barrier layer. The construction of
Structures 16 can, as described previously, comprise any suitable conductive material. In particular aspects, conductive structures 16 can comprise conductively-doped silicon, and in other exemplary aspects the conductive structures can comprise one or more metal silicides, such as, for example, titanium silicide. To the extent that the conductive structures comprise silicide, it can be advantageous to include the nitride-containing barrier layer 26 over the silicide. If the structures do not comprise silicide, barrier layer 26 can be omitted, or replaced with a non-barrier material, such as, for example, a composition which does not include a nitride.
One common aspect of the capacitor constructions of
A circuit device comprising rugged material formed in accordance with methodology of the present invention (such as the above-described DRAM cells) can be utilized in numerous assemblies, including, for example, computer systems and other electronic systems.
In particular aspects of the invention, memory device 408 can correspond to a memory module. For example, single in-line memory modules (SIMMs) and dual in-line memory modules (DIMMs) may be used in the implementation which utilizes the teachings of the present invention. The memory device can be incorporated into any of a variety of designs which provide different methods of reading from and writing to memory cells of the device. One such method is the page mode operation. Page mode operations in a DRAM are defined by the method of accessing a row of a memory cell arrays and randomly accessing different columns of the array. Data stored at the row and column intersection can be read and output while that column is accessed.
An alternate type of device is the extended data output (EDO) memory which allows data stored at a memory array address to be available as output after the addressed column has been closed. This memory can increase some communication speeds by allowing shorter access signals without reducing the time in which memory output data is available on a memory bus. Other alternative types of devices include SDRAM, DDR SDRAM, SLDRAM, VRAM and Direct RDRAM, as well as others such as SRAM or Flash memories.
The memory device 802 receives control signals 824 from the processor 822 over wiring or metallization lines. The memory device 802 is used to store data which is accessed via I/O lines. It will be appreciated by those skilled in the art that additional circuitry and control signals can be provided, and that the memory device 802 has been simplified to help focus on the invention. At least one of the processor 822 or memory device 802 can include a DRAM cell of the type described previously in this disclosure.
The various illustrated systems of this disclosure are intended to provide a general understanding of various applications for the circuitry and structures of the present invention, and are not intended to serve as a complete description of all the elements and features of an electronic system using memory cells in accordance with aspects of the present invention. One of ordinary skill in the art will understand that the various electronic systems can be fabricated in single-package processing units, or even on a single semiconductor chip, in order to reduce the communication time between the processor and the memory device(s).
Applications for memory cells can include electronic systems for use in memory modules, device drivers, power modules, communication modems, processor modules, and application-specific modules, and may include multilayer, multichip modules. Such circuitry can further be a subcomponent of a variety of electronic systems, such as a clock, a television, a cell phone, a personal computer, an automobile, an industrial control system, an aircraft, and others.
In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.
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|U.S. Classification||257/303, 257/E21.649, 257/309, 257/E21.013, 438/255, 257/E21.019, 257/311, 257/306, 257/E31.004, 257/317, 438/254|
|International Classification||H01L29/94, H01L21/8242, H01L27/108, H01L21/02|
|Cooperative Classification||Y10S438/964, H01L28/82, H01L28/84, H01L27/10852, H01L27/10817, H01L28/91, H01L27/10855|
|European Classification||H01L28/84, H01L28/91, H01L27/108F2M, H01L28/82, H01L27/108M4B2|
|Dec 4, 2007||CC||Certificate of correction|
|Feb 24, 2011||FPAY||Fee payment|
Year of fee payment: 4
|May 8, 2015||REMI||Maintenance fee reminder mailed|
|Sep 25, 2015||LAPS||Lapse for failure to pay maintenance fees|
|Nov 17, 2015||FP||Expired due to failure to pay maintenance fee|
Effective date: 20150925